The study of two-person relationships is pivotal to the fostering of mental health. Presumably pathology emanates, in part, from dysfunctional relationships with parents, siblings, and spouse and rehabilitation emerges from relationships with change agents, friends, and family members. The Social Relations Model represents a natural and intuitively appealing approach to the study of two-person relationships. A person's behavior is assumed to be a function of the person, his or her partner, and the unique relationship that the two have established. With the model, variance can be partitioned into individual and dyadic components and reciprocity of interpersonal behavior can be measured. Proposed is to extend the Social Relations Model to allow for the study of special dyads such as married couples and close friends. The model will allow for new ways of measuring the ways in which close relationships differ from ordinary relationships. Also proposed is the study of self-perception and its relationship to other perception. It may be possible to measure self-perception through peer perception. Also to be investigated are procedures for separating error and relationship variance and procedures for measuring the effects of situational variables. The work consists of analytic solutions, software development, and data analysis applications. The data sets employed are from the areas of interpersonal attraction, nonverbal communication, leadership, person perception, self-disclosure, and social behavior.